Method for connecting a first object to a second object which has a partly open structure

ABSTRACT

Method for connecting a first object to a second object along a common contact surface, wherein the first object comprises at the location of the contact surface a portion for a connecting means to be applied, which portion is accessible along an edge zone of or via at least one opening in the second object, by means of thermal spraying of particles of a material suitable as connecting means onto the first object along the edge zone of respectively via the at least one opening in the second object in a quantity such that in solidified state the deposited material particles form a connection between the first and the second object, in addition to a convector element manufactured according to this method.

This is a continuation application of Ser. No. 09/600,634 filed on Jul.20, 2000 now U.S. Pat. No. 6,328,199, which is a 371 of PCT/NL99/00025,filed Jan. 15, 1999.

The invention relates to a method for connecting a first object to asecond object along a common contact surface, wherein the first objectcomprises at the location of the contact surface a portion for aconnecting means to be applied, which portion is accessible along anedge zone of or via at least one opening in the second object.

According to the prior art solderable metal objects which have to bemutually connected are usually soldered. The soldering process requiresa good metallic contact between the objects for soldering, which musteach be brought in their entirety to a temperature suitable forsoldering, for instance 250° C. This requirement results in considerableenergy costs, particularly in the case of large objects or objects whichare soldered according to a continuous process in a belt furnace. Duringsoldering a solder material is used which produces a harmful vapour atsaid soldering temperature with all the associated risks or adverseconsequences for health and environment.

A further drawback of the soldering technique is that it is inherentlylimited to solderable materials and is unsuitable for connecting a metalsuch as for instance aluminum, which is a particularly suitable metalfor many applications because of its low density and good thermalconductivity.

Another drawback of the soldering technique is that, as a result of theuse of solder flux, soldered connections are extremely susceptible togalvanic corrosion in determined weather conditions, so that solderedconnections are insufficiently durable under determined conditions.

It is an object of the invention to provide a method for durableconnection of objects, in particular metal objects, according to whichit is not necessary to heat each of the objects in their entirety andwherein no harmful vapour is released and use of which is not limited toobjects of solderable metals.

These objects are achieved and other advantages gained with a method ofthe type stated in the preamble, which method according to the inventioncomprises the successive steps of

(i) providing a first and a second object,

(ii) holding the first object against the second object along a commonsurface,

(iii) melting and atomizing particles of a material suitable asconnecting means, and

(iv) depositing along the edge zone respectively via the at least oneopening the material particles in molten state on the first object andon the edge zone respectively the edges of said opening, in a quantitysuch that in

solidified state the deposited material particles form a connectionbetween the first and the second object.

Melting and atomizing of particles is per se known as thermal spraying.Thermal spraying is a technique wherein a layer of a material, generallya metal, is applied to a substrate by melting the material and atomizingit in fine droplets in the direction of the object for covering. Thermalspraying is used to provide materials with a coating, for instance tomake the surface of these materials wear-resistant and/orcorrosion-resistant.

Surprisingly, it has now been found that the per se known technique ofthermal spraying is not only suitable for coating a single object, butis likewise suitable for connecting two objects.

The advantages of connecting objects by means of thermal spraying arenumerous when compared to soldering.

It is not necessary to bring both objects in their entirety to asoldering temperature, which results in a considerable saving of energycosts. Furthermore, in the connection by means of thermal spraying theeffective contact surface between the objects for connecting is largerthan in the case of a corresponding solder connection.

Further cost-savings are realized in that the connecting materialrequired for a connection according to the spraying technique isappreciably cheaper that the connecting material required for acomparable solder connection.

A further advantage of the connecting technique according to theinvention is the absence of harmful vapours.

A further significant advantage is the possibility of also mutuallyconnecting objects of materials which are not solderable or onlysolderable with difficulty, for instance aluminum.

The connections made according to the invented method arecorrosion-resistant and durable and, with a suitable choice of material,have very good heat-conducting properties.

The methods for melting and atomizing particles designated by the termthermal spraying can be distinguished into atomizing of already liquidmaterial from a crucible, so-called wire spraying wherein a wire of thematerial for spraying is melted in a gas-oxygen flame, an electric arcor a plasma torch and is subsequently atomized with air or another gas,and so-called powder spraying, wherein the material for spraying issupplied in powder form to the flame, arc or torch and is subsequentlyatomized.

In accordance with the manner of supplying the heat required for meltingthe material for atomizing, methods for thermal spraying can be furthersub-divided into flame spraying with a gas-oxygen flame, electric arcspraying, plasma spraying and other methods for thermal spraying.

In an advantageous embodiment the method according to the inventioncomprises arc or plasma spraying in the third step (iii).

In another advantageous embodiment the third step (iii) comprises powderor wire spraying.

A material suitable as connecting means is for instance a material whichcan be atomized with a flame spraying process.

The material suitable as connecting means has for 5 instance a meltingpoint or an upper limit of a melting range at a temperature below 2400°C., preferably at a temperature below 600° C., more preferably at atemperature below 150° C.

It has been found that the material suitable as connecting means in amethod according to the invention contains at least one of the metalsaluminum, chromium, iron, nickel, copper, zinc, molybdenum, palladium,silver, indium, tin, antimony, lead or an alloy of at least one of thesemetals.

The invention is applied in advantageous manner when the portion of thefirst object accessible for the connecting means is porous, wherein thepores have dimensions such that the material deposited and solidified inthe fourth step (iv) forms a mechanical connection due to anchoring ofthis material in these pores.

The porous portion is herein obtained for instance by forming an alloylayer of a material suitable as connecting means with a portion of thefirst object.

In yet another embodiment the porous portion is obtained by forming acoating layer of a material suitable as connecting means on a portion ofthe first object.

Yet another advantageous method has the feature that the second step(ii) is performed immediately preceding and synchronously with the thirdstep (iii). This method can for instance be applied in a continuousprocess, wherein the first object is fixed against the second object bya pressure roller on the first object directly preceding the locationwhere the connection is thermally sprayed.

The method according to the invention is particularly suitable forconnecting objects of which at least the first object or the secondobject is manufactured substantially from a metal at the location of thecontact surface.

The metal is for instance selected from the group comprising aluminum,chromium, iron, nickel, copper, molybdenum, palladium, silver, indium,gold, tungsten and an alloy of at least one of these metals.

The method according to the invention provides particular advantages inthe connection of a tubular object, for instance a liquid conduit pipe,to a gauze-like support structure, for instance a heat-conducting metalgauze, along a common contact surface, wherein according to theinvention in the fourth step (iv) metal particles are deposited onto thetubular object via the mesh in the gauze-like support.

It is thus possible in simple and exceptionally inexpensive manner tomanufacture a convector element which can for instance be arranged in asystem ceiling for the purpose of space heating. The investment costsfor an installation for manufacturing such a convector element, whereinthe liquid conduit pipe is connected to the support structure by meansof thermal spraying according to the invention, are appreciably lowerthan the costs of a corresponding installation for soldering.

The process costs, i.e. the costs of the connecting material and thecosts of gas and electricity, are considerably lower in the case ofconnection by means of thermal spraying than when a similar connectionis made by means of soldering, while in thermal spraying no harmfulvapours with an environmental impact are released and the resultingconnection is corrosion-resistant and therefore durable.

The invention further relates to a convector element comprising aheat-conducting metal gauze and at least one liquid conduit pipeconnected thereto which is obtained with a method according to theinvention.

The present invention will be elucidated hereinbelow with reference tothe annexed drawings.

In the drawings

FIG. 1a is a broken-away perspective view of a portion of a convectorelement according to the prior art, shown in a position wherein theliquid conduit pipe is situated on the upper side of the metal gauze,

FIG. 1b shows in perspective view a detail of the underside of theelement of FIG. 1a,

FIG. 2a is a broken-away perspective view of a portion of a convectorelement manufactured according to the invented method, shown in aposition wherein the liquid conduit pipe is situated on the underside ofthe metal gauze, and

FIG. 2b is a perspective view of a detail of the element of FIG. 2a,shown in corresponding position.

Corresponding components in the drawing are designated with the samereference numerals.

FIG. 1a shows a portion of a convector element 1, for instance intendedfor mounting in a ceiling, wherein copper liquid conduit pipes 3 aresoldered against a copper gauze 2 (“copper expanded material”) inaccordance with a known soldering technique. Prior to soldering thepipes 3 are fixed against copper gauze 2 using metal wires 4.

FIG. 1b shows a detail of FIG. 1a from the underside at the location ofa conduit pipe 3. At the location of the contact surface between gauze 2and pipes 3 solder material (not visible in the figure) is situated in aquantity such the meshes 5 in gauze 2 are open over the whole surface ofthe gauze and conduit pipes 3 are visible over their whole lengththrough gauze 2.

FIG. 2a shows a portion of a convector element 6 assembled from coppergauze 2, against which conduit pipes 3 are arranged with a connectingmethod according to the invention by thermally spraying connectingmaterial through meshes 5 in gauze 2 at the location of pipes 3 in thedirection of the arrows 7. The figure further shows fixing wires 4 whichare used to fix pipes 3 against gauze 2 prior to and during the thermalspraying. In contrast to soldering, it is relatively simple in the caseof thermal spraying in a continuous process to fix the pipes against theguaze in alternative manner, for instance by applying a pressure rollerdirectly preceding the location where the connection is thermallysprayed.

FIG. 2b shows a detail of element 6 of FIG. 2a at the position of aconduit pipe 3, which is not visible as such but the position of whichis marked by a strip 8 of thermally sprayed connecting material whichcompletely fills meshes 5 at the location of said pipe.

What is claimed is:
 1. A method for connecting a first object to asecond object along a common contact surface, wherein the first objectcomprises, at the location of the contact surface, a portion for a meansfor connecting to be applied, said portion accessible along at least oneedge zone of the second object, the method comprising: providing a firstobject and a second object; holding the first object against the secondobject along the common contact surface; melting and atomizing particlesof a material comprising the means for connecting; and depositing alongthe at least one edge zone the particles in molten state on the firstobject and on the edge zone respectively the edges of said opening, in aquantity such that in solidified state the deposited material particlesform a connection between the first object and the second object,wherein the melting and atomizing comprises at least one offlame-spraying with a gas-oxygen flame and electric-arc spraying.
 2. Themethod of claim 1, wherein the melting and atomizing further comprisesat least one of powder spraying and wire spraying.
 3. The method ofclaim 1, wherein the material suitable as the means for connecting has amelting point or an upper limit of a melting range at a temperaturebelow 2400° C.
 4. The method of claim 3, wherein the melting point orthe upper limit of a melting range lies at a temperature below 600° C.5. The method of claim 3, wherein the melting point or the upper limitof a melting range lies at a temperature below 150° C.
 6. The method ofclaim 1, wherein the material suitable as the means for connectingcontains at least one of aluminum, chromium, iron, nickel, copper, zinc,molybdenum, palladium, silver, indium, tin, antimony, lead, and alloysthereof.
 7. The method of claim 1, wherein the portion of the firstobject accessible for the means for connecting is porous, and whereinpores have dimensions such that the material deposited and solidifiedforms a mechanical connection through interlocking of the materialdeposited and solidified and the pores.
 8. The method of claim 7,wherein the porous portion is obtained by forming an alloy layer of amaterial suitable as the means for connecting with a portion of thefirst object.
 9. The method of claim 7, wherein the porous portion isobtained by forming a coating layer of a material suitable as the meansfor connecting on a portion of the first object.
 10. The method of claim1, wherein the holding is performed immediately preceding the meltingand atomizing.
 11. The method of claim 1, wherein the first object, atthe location of the contact surface, is manufactured substantially froma metal.
 12. The method of claim 1, wherein the second object, at thelocation of the contact surface, is manufactured substantially from ametal.
 13. The method of claim 11, wherein the metal comprises at leastone of aluminum, chromium, iron, nickel, copper, molybdenum, palladium,silver, indium, gold, tungsten, and alloys thereof.